Alginate microencapsulated human hepatocytes for the treatment of acute liver failure in children.

BACKGROUND & AIMS: Liver transplantation (LT) is the most effective treatment for patients with acute liver failure (ALF), but is limited by surgical risks and the need for life-long immunosuppression. Transplantation of microencapsulated human hepatocytes in alginate is an attractive option over whole liver replacement. The safety and efficacy of hepatocyte microbead transplantation have been shown in animal models. We report our experience of this therapy in children with ALF treated on a named-patient basis. METHODS: Clinical grade human hepatocyte microbeads (HMBs) and empty microbeads were tested in immunocompetent healthy rats. Subsequently, 8 children with ALF, who were awaiting a suitable allograft for LT, received intraperitoneal transplantation of HMBs. We monitored complications of the procedure, assessing the host immune response and residual function of the retrieved HMBs, either after spontaneous native liver regeneration or at the time of LT. RESULTS: Intraperitoneal transplantation of HMBs in healthy rats was safe and preserved synthetic and detoxification functions, without the need for immunosuppression. Subsequently, 8 children with ALF received HMBs (4 neonatal haemochromatosis, 2 viral infections and 2 children with unknown cause at time of infusion) at a median age of 14.5 days, range 1 day to 6 years. The procedure was well tolerated without complications. Of the 8 children, 4 avoided LT while 3 were successfully bridged to LT following the intervention. HMBs retrieved after infusions (at the time of LT) were structurally intact, free of host cell adherence and contained viable hepatocytes with preserved functions. CONCLUSION: The results demonstrate the feasibility and safety of an HMB infusion in children with ALF. LAY SUMMARY: Acute liver failure in children is a rare but devastating condition. Liver transplantation is the most effective treatment, but it has several important limitations. Liver cell (hepatocyte) transplantation is an attractive option, as many patients only require short-term liver support while their own liver recovers. Human hepatocytes encapsulated in alginate beads can perform the functions of the liver while alginate coating protects the cells from immune attack. Herein, we demonstrated that transplantation of these beads was safe and feasible in children with acute liver failure.

Cryopreservation of Hepatocyte Microbeads for Clinical Transplantation.

Intraperitoneal transplantation of hepatocyte microbeads is an attractive option for the management of acute liver failure. Encapsulation of hepatocytes in alginate microbeads supports their function and prevents immune attack of the cells. Establishment of banked cryopreserved hepatocyte microbeads is important for emergency use. The aim of this study was to develop an optimized protocol for cryopreservation of hepatocyte microbeads for clinical transplantation using modified freezing solutions. Four freezing solutions with potential for clinical application were investigated. Human and rat hepatocytes cryopreserved with University of Wisconsin (UW)/10% dimethyl sulfoxide (DMSO)/5% (300 mM) glucose and CryoStor CS10 showed better postthawing cell viability, attachment, and hepatocyte functions than with histidine-tryptophan-ketoglutarate/10% DMSO/5% glucose and Bambanker. The 2 freezing solutions that gave better results were studied with human and rat hepatocytes microbeads. Similar effects on cryopreserved microbead morphology (external and ultrastructural), viability, and hepatocyte-functions post thawing were observed over 7 d in culture. UW/DMSO/glucose, as a basal freezing medium, was used to investigate the additional effects of cytoprotectants: a pan-caspase inhibitor (benzyloxycarbonyl-Val-Ala-dl-Asp-fluoromethylketone [ZVAD]), an antioxidant (desferoxamine [DFO]), and a buffering and mechanical protectant (human serum albumin [HSA]) on RMBs. ZVAD (60 µM) had a beneficial effect on cell viability that was greater than with DFO (1 mM), HSA (2%), and basal freezing medium alone. Improvements in the ultrastructure of encapsulated hepatocytes and a lower degree of cell apoptosis were observed with all 3 cytoprotectants, with ZVAD tending to provide the greatest effect. Cytochrome P450 activity was significantly higher in the 3 cytoprotectant groups than with fresh microbeads. In conclusion, developing an optimized cryopreservation protocol by adding cytoprotectants such as ZVAD could improve the outcome of cryopreserved hepatocyte microbeads for future clinical use.

Coculture with mesenchymal stem cells results in improved viability and function of human hepatocytes.

Hepatocyte transplantation is becoming an accepted therapy for acute liver failure, either as a bridge to liver regeneration or to organ transplantation. Hepatocytes provide liver function in place of the failing organ. The maintenance of sufficient viability and function of the transplanted hepatocytes is a concern. There is a lot of recent interest in mesenchymal stem cells (MSCs) for the provision of structural and trophic support to hepatocytes, but few studies currently use primary human hepatocytes. The aim of this study was to investigate if coculture of human MSCs with cryopreserved human hepatocytes may improve their function and viability, thus with potential for cellular therapy of liver disease. MSCs were isolated from human umbilical cord or adipose tissue. Hepatocytes were isolated from donor organs unsuitable for transplantation. MSCs and hepatocytes were cocultured in both direct and indirect contact. Conditioned medium (CM) from cocultured MSCs and hepatocytes was also used on hepatocytes. Viability and liver-specific function were compared between test and controls. Human hepatocytes that were cocultured directly with MSCs demonstrated improved production of albumin from day 5 to day 25 of culture. This effect was most prominent at day 15. Likewise, urea production was improved in coculture from day 5 to 25. Indirect coculture demonstrated improved albumin production by day 4 (1,107 ng/ml) versus hepatocyte monoculture (940 ng/ml). Hepatocytes in CM demonstrated a nonsignificant improvement in function. The viability of cocultured hepatocytes was superior to that of monocultured cells with up to a 16% improvement. Thus, coculture of human hepatocytes with MSCs demonstrates both improved function and viability. The effect is seen mainly with direct coculture but can also be seen in indirect culture and with CM. Such coculture conditions may convey major advantages in hepatocyte survival and function for cell transplantation.

Alginate microencapsulated hepatocytes optimised for transplantation in acute liver failure.

BACKGROUND AND AIM: Intraperitoneal transplantation of alginate-microencapsulated human hepatocytes is an attractive option for the management of acute liver failure (ALF) providing short-term support to allow native liver regeneration. The main aim of this study was to establish an optimised protocol for production of alginate-encapsulated human hepatocytes and evaluate their suitability for clinical use. METHODS: Human hepatocyte microbeads (HMBs) were prepared using sterile GMP grade materials. We determined physical stability, cell viability, and hepatocyte metabolic function of HMBs using different polymerisation times and cell densities. The immune activation of peripheral blood mononuclear cells (PBMCs) after co-culture with HMBs was studied. Rats with ALF induced by galactosamine were transplanted intraperitoneally with rat hepatocyte microbeads (RMBs) produced using a similar optimised protocol. Survival rate and biochemical profiles were determined. Retrieved microbeads were evaluated for morphology and functionality. RESULTS: The optimised HMBs were of uniform size (583.5±3.3 µm) and mechanically stable using 15 min polymerisation time compared to 10 min and 20 min (p<0.001). 3D confocal microscopy images demonstrated that hepatocytes with similar cell viability were evenly distributed within HMBs. Cell density of 3.5×10(6) cells/ml provided the highest viability. HMBs incubated in human ascitic fluid showed better cell viability and function than controls. There was no significant activation of PBMCs co-cultured with empty or hepatocyte microbeads, compared to PBMCs alone. Intraperitoneal transplantation of RMBs was safe and significantly improved the severity of liver damage compared to control groups (empty microbeads and medium alone; p<0.01). Retrieved RMBs were intact and free of immune cell adherence and contained viable hepatocytes with preserved function. CONCLUSION: An optimised protocol to produce GMP grade alginate-encapsulated human hepatocytes has been established. Transplantation of microbeads provided effective metabolic function in ALF. These high quality HMBs should be suitable for use in clinical transplantation.

Ex vivo magnetic resonance imaging of transplanted hepatocytes in a rat model of acute liver failure.

Hepatocyte transplantation is being evaluated as an alternative to liver transplantation. However, the fate of hepatocytes after transplantation is not well defined. The aims of the study were to improve hepatocyte labeling in vitro using superparamagnetic iron oxide nanoparticles (SPIOs) and to perform in vivo experiments on tracking labeled cells by magnetic resonance imaging (MRI). Human and rat hepatocytes were labeled in vitro for 16 h with clinically approved SPIOs (12.5 µg Fe/ml) and protamine sulfate (3 µg/ml) as a transfection agent. Increased cellular iron uptake was obtained, and cell viability and function were shown not to be affected by labeling. Labeled cells (2,000/µl) could be detected on T2-weighted images in vitro using a 7T MR scanner. In a rat model of acute liver failure (ALF), female recipients received intrasplenic transplantation of 2 × 10(7) male rat hepatocytes 28-30 h after intraperitoneal injection of d-galactosamine (1.2 g/kg). There were four groups (n = 4 each): vehicle injection, injection of freshly isolated cells labeled with CM-DiI, injection of cultured cells labeled with CM-DiI, and injection of cultured cells labeled with both SPIOs and CM-DiI. Ex vivo T2*-weighted gradient-echo images at 7T MRI were acquired at day 7 post-ALF induction. Six days after transplantation, SPIOs were detected in the rat liver as a decrease in the MRI signal intensity in the surviving animals. Histologically, most of the SPIOs were located in Kupffer cells, indicating clearance of labeled hepatocytes. Furthermore, labeled cells could not be detected in the liver by the fluorescent dye or by PCR for the Y-chromosome (Sry-2 gene). In conclusion, optimum conditions to label human hepatocytes with SPIOs were established and did not affect cell viability or metabolic function and were sufficient for in vitro MRI detection. However, the clearance of hepatocytes after transplantation limits the value of MRI for assessing long-term hepatocyte engraftment.

Use of indocyanine green for functional assessment of human hepatocytes for transplantation.

BACKGROUND/OBJECTIVE: Hepatocyte transplantation is a promising alternative to liver transplantation in children with liver metabolic disorders and acute liver failure. Currently, it is difficult to assess rapidly hepatocyte function before transplantation. The aim of this study was to investigate whether the uptake and release of indocyanine green (ICG) by hepatocytes could be used. METHODS: Human hepatocytes (10(6) cells) isolated from unused donor livers were incubated at 37°C for 30 minutes with ICG (0-2mg/mL) in both cell suspension and on collagen-coated culture plates. Cells were then incubated in medium without ICG for 3 hours with supernatants collected at 1, 2 and 3 hours for measurement of ICG release. Cell viability was determined by trypan blue exclusion, (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay (mitochondrial dehydrogenase activity) and sulforhodamine B (SRB) assay (cell attachment). HepG2 cells were also used. RESULTS: ICG was taken up and secreted by hepatocytes with the release reaching a plateau level soon after 1 hour. Concentrations of ICG > 1.0mg/mL had toxic effects on hepatocytes. Hepatocytes incubated with 1.0mg/mL ICG had higher mitochondrial dehydrogenase activity compared to 0.5mg/mL ICG or control cells (0.025 ± 0.0004 OD unit vs. 0.019 ± 0.0008 OD unit or 0.020 ± 0.002 OD unit, p<0.05). Incubation of HepG2 cells with ICG reduced albumin production (98.9 ± 0.02 ng/mL, 66.6 ± 0.05 ng/mL and 39.1 ± 0.4 ng/mL for control cells, and 0.5mg/mL and 1.0mg/mL ICG, respectively), and decreased [(3)H]-thymidine incorporation in a dose-dependent manner. Addition of taurine (20mM) to plated hepatocytes gave greater release of ICG and hepatocyte attachment compared to controls, at all ICG concentrations (SRB 1.360 ± 0.083 optical density units vs. 0.908 ± 0.159 optical density units, p=0.011 at 1.0mg/mL). CONCLUSION: With further refinement, ICG could be used to develop a rapid assay for assessment of the function of isolated human hepatocytes.

Cryopreservation of human hepatocytes for clinical use.

Cryopreservation of hepatocytes is important for use both in research and for clinical application in hepatocyte transplantation. Cryopreservation causes damage to hepatocytes with the result that cell viability and function is reduced on thawing compared to fresh cells. There are many different protocols reported for freezing human hepatocytes mainly using DMSO as cryoprotectant. In this chapter the current detailed protocols used for cryopreservation and thawing of human hepatocytes for cell transplantation at the Cell Isolation Unit at King's College Hospital, London, are described. All procedures must be performed in a clean GMP environment using materials and reagents which are of pharmaceutical grade. The cryopreservation media is UW solution with added 300 mM glucose containing 10% DMSO and the thawing solution is EMEM containing 2% HSA. Freezing is performed in a controlled-rate freezer using a stepwise cooling programme.

N-acetylcysteine improves the viability of human hepatocytes isolated from severely steatotic donor liver tissue.

Hepatocyte transplantation is dependent on the availability of good quality human hepatocytes isolated from donor liver tissue. Hepatocytes obtained from livers rejected for transplantation on the grounds of steatosis are often of low viability and not suitable for clinical use. The aim of this study was to evaluate the effects of the antioxidant N-acetylcysteine (NAC) on the function of hepatocytes isolated from steatotic donor livers. Human hepatocytes were isolated from 10 severely steatotic (>60%) donor livers rejected for transplantation. The left lateral segment of the donor liver was dissected into two equal size pieces and randomized to NAC or control. NAC (5 mM) was added to the first perfusion buffer of the standard collagenase digestion technique. Cells from tissues perfused with NAC had a significantly higher mean viability (81.1 ± 1.7% vs. 66.0 ± 4.7%; p = 0.003) and cell attachment (1.08 ± 0.26 vs. 0.67 ± 0.18 OD units; p = 0.012). Addition of NAC during isolation of human hepatocytes from steatotic donor liver tissue significantly improved the outcome of cell isolation. Further studies are needed to investigate the mechanism(s) of this effect. Incorporation of NAC in the hepatocyte isolation protocol could increase the availability of hepatocytes for transplantation.

Optimization of the cryopreservation and thawing protocol for human hepatocytes for use in cell transplantation.

Cryopreservation of human hepatocytes is important for their use in hepatocyte transplantation. On thawing, cryopreserved hepatocytes often have reduced viability and metabolic function in comparison with fresh cells. The aim of this study was to modify the different steps in the standard cryopreservation procedure in an attempt to improve the overall outcome. Human hepatocytes with a viability of 69% +/- SD 16% were isolated from donor livers with a collagenase perfusion technique. Different cell densities, concentrations, rates, and methods of addition of dimethyl sulfoxide were tested for the freezing solution. Modified controlled-rate freezer programs were tested to obtain a linear decrease in the temperature. Once they were frozen, the storage time and thawing method for hepatocytes were investigated. The effects on thawed cell viability and attachment, lactate dehydrogenase release, cytochrome P450 1A1/2 activity, and albumin synthesis were determined. The results were used to produce an improved cryopreservation protocol suitable for good manufacturing practice conditions. With a cell density of 10(7) cells/mL in University of Wisconsin solution containing 300 mM glucose, 10% (vol/vol) dimethyl sulfoxide was added dropwise over 5 minutes, and was immediately frozen. Thawing was done rapidly at 37 degrees C, and dilution was performed with Eagle's minimum essential medium containing 300 mM glucose and 4% human serum albumin. Hepatocytes could be stored at -140 degrees C without significant further loss of function for up to 3 years. With this protocol, hepatocytes had a viability of 52% +/- 9%, an attachment efficiency of 48% +/- 8%, and lactate dehydrogenase leakage of 17% +/- 4%. This protocol is currently in use to cryopreserve hepatocytes for use in cell transplantation at our center.

Experience of microbiological screening of human hepatocytes for clinical transplantation.

Hepatocyte transplantation is being used in patients with liver-based metabolic disorders and acute liver failure. Hepatocytes are isolated from unused donor liver tissue under GMP conditions. Cells must be free of microbiological contamination to be safe for human use. The experience of microbiological screening during 72 hepatocyte isolation procedures at one center is reported. Samples were taken at different stages of the process and tested using a blood culture bottle system and Gram stain. Bacterial contamination was detected in 37.5% of the UW organ preservative solutions used to transport the liver tissue to the Cell Isolation Unit. After tissue processing the contamination was reduced to 7% overall in the final hepatocyte product, irrespective of the presence of initial contamination of the transport solution. The most common organisms recovered were coagulase-negative staphylococci, a skin commensal. A total of 41 preparations of fresh or cryopreserved hepatocytes were used for cell transplantation in children with liver-based metabolic disorders without any evidence of sepsis due to infusion of hepatocytes. In conclusion, the incidence of bacterial contamination of the final product was low, confirming the suitability of the organs used, hepatocyte isolation procedure, and the environmental conditions of the clean room.

Microbiological monitoring of hepatocyte isolation in the GMP laboratory.

For clinical hepatocyte transplantation, cells need to be prepared in a sterile GMP environment. Strict regulations are in place that set the standard for this environment that cells are prepared in. These regulations control all aspects of the environment. In the United Kingdom, the laboratory must have a licence from the Human Tissue Authority to prepare cell for clinical administration. The physical parameters such as air quality, pressure, temperature and microbiology counts have to be monitored regularly usually through direct measurement. Described here are the methods for microbial monitoring of the laboratory environment and the isolated cell preparations.

Liver after hepatocyte transplantation for liver-based metabolic disorders in children.

There are limited data regarding donor hepatocyte engraftment into recipient liver after human hepatocyte transplantation (HHTx). We reviewed the explant livers of seven children with metabolic disorders [ornithine-transcarbamylase deficiency (one), coagulation factor VII deficiency (three), Crigler-Najjar syndrome (one), progressive familial intrahepatic cholestasis type 2 (PFIC-2) deficiency (two)] who received allograft hepatocytes by intraportal infusion with improvement in phenotype, although all later underwent liver transplantation (LT). Immunohistochemistry for bile salt export protein (BSEP) in the PFIC-2 patients and genetic typing following laser capture microdissection (LCM) of liver cells in the others were used to identify donor hepatocytes in recipient explant livers. Explant livers usually showed a preserved lobular architecture. In one patient, hepatocytes were identified inside portal vein thrombi. No donor hepatocytes in liver cell plates were identified immunohistochemically or by genetic typing. HHTx was generally followed by partial recovery of metabolic function; the procedure was well tolerated; any increase in portal vein pressure was transient. Hepatocytes were identified in portal vein thrombi, even months after portal vein infusion. Further studies are needed to monitor donor hepatocytes in vivo, to quantify better the efficacy of the procedure and to find ways of improving engraftment and function.

Cryopreservation-induced nonattachment of human hepatocytes: role of adhesion molecules.

Good quality cryopreserved human hepatocytes are becoming an important source for clinical hepatocyte transplantation. However, the process of cryopreservation leads to both structural and functional impairment of hepatocytes. The aim of this study was to investigate the mechanisms of cryopreservation-induced nonattachment in human hepatocytes. Hepatocytes were cryopreserved after isolation from unused donor liver tissue. Cell attachment to collagen-coated plates was measured. A cDNA gene array system for 96 cell adhesion-related molecules was used to determine mRNA expression in fresh and cryopreserved hepatocytes. Two cell adhesion molecule proteins were investigated further: beta1-integrin, a cell-matrix adhesion molecule, and E-cadherin, a cell-cell adhesion molecule. Attachment efficiency was significantly decreased after cryopreservation of human hepatocytes. Twenty-two genes were downregulated after cryopreservation including integrins, cadherins, catenins, and matrix metalloproteinases (MMPs). Beta1-Integrin gene and protein expression were significantly decreased in cultured cryopreserved hepatocytes compared to fresh hepatocytes. There was a significant correlation between loss of beta1-integrin and attachment in cryopreserved cells. Degradation of E-cadherin was increased in cryopreserved hepatocytes. The process of cryopreservation leads to downregulation of cell adhesion molecules at the gene and the cellular level. New cryopreservation protocols are needed to prevent these effects on cell attachment.

Analysis of the effects of cryopreservation on rat hepatocytes using SELDI-TOF mass spectrometry.

Successful cryopreservation of hepatocytes is essential to the future of hepatocyte transplantation as a treatment for liver disease, and also for the improved in vitro use of hepatocytes for research. However, hepatocyte function is adversely affected by even the best cryopreservation protocols. To investigate possible mechanisms for these changes, total cell lysates were prepared from fresh and cryopreserved rat hepatocytes and the proteome profiles compared using SELDI-TOF-MS ProteinChip technology. In addition, in vitro functional assays (viability, attachment efficiency, and lactate dehydrogenase leakage) were performed on the corresponding fresh and cryopreserved hepatocytes. Sixty-one peptides were identified as being significantly changed after cryopreservation. Thirty-seven peaks were significantly increased and 24 were significantly decreased after cryopreservation. The peak intensity of a number of these peptides was found to correlate with the in vitro function of the hepatocytes. Seven peptides correlated with in vitro function after cryopreservation and 10 peptides correlated with both fresh and cryopreserved function. The peptides significantly decreased after cryopreservation could include cytosolic enzymes or cofactors, which leaked out of the cells due to cryopreservation-induced membrane damage. The peptides significantly increased after cryopreservation could be retained products of cleavage of larger intracellular polypeptides and proteins or the result of aggregation of peptides caused by physical changes in the cell due to the cryopreservation process. Proteome profiling using SELDI-TOF-MS could be a useful tool to assess the effects of isolation and cryopreservation of hepatocytes, particularly if the findings are extended to human hepatocytes.

Isolation of hepatocytes from livers from non-heart-beating donors for cell transplantation.

One of the limitations to hepatocyte transplantation is the restricted availability of donor liver tissue. The aim of this study was to evaluate livers from non-heart-beating donors (NHBDs) as a source of hepatocytes for cell transplantation. A total of 20 livers/segments obtained from NHBD were perfused under good manufacturing practices using a standard collagenase digestion method. The donor liver median warm ischemia time was 15 minutes (range, 11-40 minutes), and cold ischemia time was 13 hours (range, 6-30 hours) prior to cell isolation. The cell viability of the hepatocytes obtained was 52% (1-81%), with a yield of 2.2 x 10(6)(0.2-29.7 x 10(6)) cells per gram of tissue. There was a significant negative correlation between hepatocyte viability and length of both warm ischemia (r = -0.544, P = 0.013) and cold ischemia (r = -0.510, P = 0.022). Preliminary experiments were performed on the viability testing of NHBD livers based on digestion of needle biopsies with collagenase and assessment of the hepatocytes produced. Two of the NHBD cell preparations, which had been cryopreserved, were used as part of a series of cell infusions for hepatocyte transplantation. A 3.5-yr-old girl with Crigler-Najjar syndrome type I received 9.7 x 10(8) NHBD hepatocytes (viability on thawing, 65%), and a 4-month-old boy with inherited clotting factor VII deficiency received 5.0 x 10(8) hepatocytes (viability, 57%). In conclusion, hepatocytes suitable for cell transplantation can be obtained from NHBD livers. Higher viability values may be obtained if both warm and cold ischemia times of donor liver can be reduced prior to processing.

Preincubation of rat and human hepatocytes with cytoprotectants prior to cryopreservation can improve viability and function upon thawing.

Cryopreservation of human hepatocytes is important for the treatment of liver disease by hepatocyte transplantation and also for the use of hepatocytes as an in vitro model of the liver. One factor in the success of cryopreservation is the quality of cells before freezing. Preincubation of hepatocytes with cytoprotective compounds to allow recovery from the isolation process prior to cryopreservation, such as those that will boost cellular adenosine triphosphate (ATP) content or antioxidants, may improve the viability and function of cells upon thawing. Rat hepatocytes were used to investigate the effects of preincubation with 10 compounds: precursors (glucose, fructose, glutathione, and S-adenosyl-L-methionine), antioxidants (ascorbic acid and alpha-lipoic acid), and compounds with multiple effects (N-acetylcysteine, pentoxifylline, prostaglandin E1, and tauroursodeoxycholic acid). Human hepatocytes were then used to investigate 5 of the original 10 compounds (glucose, fructose, alpha-lipoic acid, S-adenosyl-L-methionine, and pentoxifylline). Glucose preincubation (100 - 300 mM) improved the viability and attachment efficiency of rat hepatocytes and improved the viability and reduced lactate dehydrogenase (LDH) leakage of human hepatocytes. Fructose preincubation (100 - 300 mM) improved the viability and attachment efficiency of rat hepatocytes and improved the attachment efficiency of human hepatocytes. alpha-lipoic acid preincubation (0.5 - 5 mM) improved the viability and attachment efficiency of both rat and human hepatocytes. At a concentration of 2.5 mM alpha-lipoic acid also improved the albumin production of human hepatocytes. In conclusion, preincubation of hepatocytes prior to cryopreservation can improve the viability and function of thawed cells and may provide a method of obtaining better-quality cryopreserved hepatocytes for transplantation.

The effects of immunosuppressive agents on the function of human hepatocytes in vitro.

Calcineurin inhibitors (tacrolimus) and steroids continue to be an important component of hepatocyte transplantation protocols, despite reports of hepatotoxicity and inhibitory effects of steroids on cell proliferation. The aim of the study was to investigate whether isolated human hepatocytes were more vulnerable to the toxicity of these agents and also to investigate their effects on hepatocyte VEGF secretion, a vascular permeability factor suggested to be involved in the cell engraftment process. Human hepatocytes were isolated from donor livers/segments rejected or unused for orthotopic liver transplantation using a collagenase perfusion technique. Hepatocytes were plated for cell function tests and to determine VEGF production. Tacrolimus (0-50 ng/ml) and methylprednisolone (0-500 ng/ml) were added to the culture media and cells incubated for 24 h. Cell metabolic activity was assessed using the MTT assay, cell number using the SRB assay, and cell attachment from hepatocyte total protein content and protein synthesis using [14C]leucine incorporation. VEGF in culture supernatants was measured by ELISA. Tacrolimus and methylprednisolone had no statistically significant inhibitory effects on metabolic activity or protein synthesis compared to controls at all concentrations of the agents tested when added after plating. There were also no significant effects on cell attachment when tacrolimus or methylprednisolone was added at the time of cell plating. There were no differences in the responses obtained when either fresh or cryopreserved hepatocytes were used. The amount of VEGF secreted by untreated hepatocytes was highly variable (0-1400 pg/10(6) cells/24 h). VEGF levels in the culture supernatant from hepatocytes isolated from < or = 20-year-old donors (687 +/- 59 pg/10(6) cells/24 h) was significantly greater than from older donors (61 +/- 7 pg/10(6) cells/24 h; p = 0.003). Tacrolimus and methylprednisolone did not significantly affect VEGF secretion by hepatocytes. Tacrolimus and methylprednisolone did not have detrimental effects on the metabolic function of human hepatocytes, cell attachment, or VEGF secretion after cell isolation.

The effects of cryopreservation on human hepatocytes obtained from different sources of liver tissue.

Successful cryopreservation of human hepatocytes is important to establish hepatocyte banks for clinical use or in vitro research. The availability of donor tissue from unused liver segments/lobes and non-heart-beating donors (NHBD) has provided newer sources of hepatocytes. The quality of hepatocytes at the time of cryopreservation is important as cells isolated from liver tissue of borderline quality may not withstand the stresses associated with cryopreservation and subsequent thawing. Human hepatocytes were cryopreserved after isolation from mainly donor tissues (n = 40). In vitro assessment of the viability and function of the fresh and thawed cryopreserved hepatocytes was performed. Viability, attachment efficiency, enzyme activity, and albumin production of hepatocytes were all significantly decreased, and LDH leakage significantly increased, on thawing after cryopreservation. The viability of cryopreserved hepatocytes isolated from tissue rejected for orthotopic liver transplantation (36 +/- 15%) was significantly lower than those isolated from tissue where part was used for liver transplantation (47 +/- 14%, p = 0.002), but there were no significant differences in functional parameters. The viability of cryopreserved hepatocytes isolated from NHBD tissue (29 +/- 9%, p = 0.001) and from steatotic donor tissue (35 +/- 11%, p = 0.019) was significantly lower than those isolated from normal donor tissue (49 +/- 14%). There was no difference in functional parameters, except for albumin production of hepatocytes from NHBD tissue (2.9 +/- 1.0 microg/h/mg protein) being significantly lower than those from normal donor tissue (4.8 +/- 2.8 microg/h/mg protein, p = 0.03). The viability and attachment efficiency of cryopreserved hepatocytes isolated from liver tissue from resections for tumors was significantly higher, and the LDH leakage significantly lower, than those isolated from all donor tissue. Hepatocytes isolated from NHBD and steatotic tissue were more vulnerable to the effects of cryopreservation. Further research is required to improve hepatocyte isolation and cryopreservation protocols for different types of liver tissue.

Preincubation of rat and human hepatocytes with cytoprotectants prior to cryopreservation can improve viability and function upon thawing.

Cryopreservation of human hepatocytes is important for the treatment of liver disease by hepatocyte transplantation and also for the use of hepatocytes as an in vitro model of the liver. One factor in the success of cryopreservation is the quality of cells before freezing. Preincubation of hepatocytes with cytoprotective compounds to allow recovery from the isolation process prior to cryopreservation, such as those that will boost cellular adenosine triphosphate (ATP) content or antioxidants, may improve the viability and function of cells upon thawing. Rat hepatocytes were used to investigate the effects of preincubation with 10 compounds: precursors (glucose, fructose, glutathione, and S-adenosyl-L-methionine), antioxidants (ascorbic acid and alpha-lipoic acid), and compounds with multiple effects (N-acetylcysteine, pentoxifylline, prostaglandin E(1), and tauroursodeoxycholic acid). Human hepatocytes were then used to investigate 5 of the original 10 compounds (glucose, fructose, alpha-lipoic acid, S-adenosyl-L-methionine, and pentoxifylline). Glucose preincubation (100-300 mM) improved the viability and attachment efficiency of rat hepatocytes and improved the viability and reduced lactate dehydrogenase (LDH) leakage of human hepatocytes. Fructose preincubation (100-300 mM) improved the viability and attachment efficiency of rat hepatocytes and improved the attachment efficiency of human hepatocytes. alpha-lipoic acid preincubation (0.5-5 mM) improved the viability and attachment efficiency of both rat and human hepatocytes. At a concentration of 2.5 mM alpha-lipoic acid also improved the albumin production of human hepatocytes. In conclusion, preincubation of hepatocytes prior to cryopreservation can improve the viability and function of thawed cells and may provide a method of obtaining better-quality cryopreserved hepatocytes for transplantation.